Isomeric Incorporation of the Haem into Monomeric Haemoglobins of Chironomus thummi thummi

Abstract

With high resolution NMR spectroscopy it was possible to detect various types of isomerisms in the monomeric component III of the hemoglobins of C. thummi. In the component III prepared from larvae of C. thummi a chemical heterogeneity occurs at the position E6 (Ile or Thr). The imidazole C-2 proton resonance of the adjacent His-E7 is split because of this alternative occupancy. From larvae of an inbreeding of the single subspecies C. thummi thummi a component III material was isolated in which the position E6 is occupied by 1 single amino acid. An additional isomerism of this hemoglobin III is produced by an isomeric incorporation of the hemegroup into the heme pocket. This isomerism was established from the complex signal pattern of the mesoproton resonances of the diamagnetic ligated hemoglobin III. Other evidence of isomerism was obtained from an analysis of the high-field proton resonances.